Flow equalizer



1957 J. c. MONAHAN FLOW EQUALIZER Filed Aug. 20, 1954 b w a M 1 w M United States Patent 07 FLOW EQUALIZER John C. Mouahan, East Detroit, Mich.

Application August 20, 1954, Serial No. 451,234

3 Claims. (Cl. 137-101) The present invention relates to an hydraulic device for equalizing the flow of fluid to and from a pair of substantially identical hydraulic piston and cylinder units so that the cylinder pistons move in and out in unison at the same speeds independently and regardless of any inequalities in the loads thereon.

In many hydraulic applications a single pump delivers fluid to a pair of cylinder and piston units in which the pistons are connected to'diiferent loads. In such assemblies it is desirable that the pistons move in and out in unison, even though there may be variations in the loads thereon and where the two loads are unequal.

According to the present invention a simplified device is provided in which a relatively simple, economical and compact unit provides the control for equalizing the flow of fluid to and from both of the cylinders regardless of inequalities in the loads thereon.

Prior to the present invention it was known to provide such control by using two separate fluid motors of identical size and coupled by a common shaft, which were interposed in the lines between the pump and the lines to the cylinders. However, such devices have not been satisfactory because of their extreme bulkiness, high cost and uncertain accuracy.

One of the primary objects of the present invention is to provide a fluid flow equalizing device of the type mentioned which is dependable and accurate in operation and which is economical to construct. A further object of the invention is to provide a compact and relatively small unit for equalizing flow in devices of the type mentioned and which takes up a relatively small space, so that its applications are many and varied.

Other objects of the invention will become apparent from the following specification, the drawings relating thereto and from the claims hereinafter set forth.

In the drawings in which like numerals are used to designate like parts in the several views throughout:

Figure l is a flow diagram illustrating the device of the present invention in one of its applications;

Fig. 2 is a diagrammatic view of the device of the present invention, illustrating the elements employed therein and illustrating the flow of fluid therethrough;

Fig. 3 is a vertical cross-sectional view of a commercial embodiment of the present invention;

Fig. 4 is a cross-sectional view taken substantially along the lines 44 of Fig. 3; and

Fig. 5 is a cross-sectional view with parts of the gear teeth removed for illustration, and taken along the line 5-5 of Fig. 3.

In the following description the elements, ports and passages are given the same indication in the diagrammatic showing of Fig. 2 and the commercial showings in Figs. 3-5 for the purpose of clear understanding, as the flow control is the same in both.

In Fig. 1, one application of the device of the present invention is illustrated in which a fluid line or conduit 1 is shown, it being understood that such conduit 1 is connected to an hydraulic pump (not shown) which 2,781,771 Patented F eb. 19, 1957 delivers fluid under pressure through line 1. A pair of substantially identical conventional cylinder and piston assemblies 2 and 3 are illustrated having loads 4 and 5, respectively, applied to the pistons. In this illustration the load 4 is shown as being substantially greater than the load 5. Fluid conduits 6 and 7 communicate respectively with the inlets of cylinders 2 and 3.

The flow control device of the present invention is generally indicated at 8 and is interposed between conduit 1 and conduits 6 and 7.

Referring to diagrammatic view 2, the flow control device 8 comprises a housing having an inlet port 9 which communicates with inlet conduit 1 and outlet ports 10 and 11, which communicate respectively with conduits 6 and 7.

Flow from the inlet port 9 is divided within thehousing into two paths for flow through a pair of inlet passages 12 and 13, which are of substantially the same size in cross section.

Intersecting cavities 14, 15 and 16 are formed within the housing and are generally circular in form and of the same diameter. Idle gears 17, 18 and 19 are disposed within the cavities 14, 15 and 16, respectively, so that gear ,18 intermeshes with gears 17 and 19 at diametrically opposed regions. The gears 17, 18 and 19 are preferably substantially identical spur gears and are disposed within the cavities, which are complementary in shape thereto, without the need of any shafts, bearings, oil seals, couplings and the like. The gears are illustrated as having solid centers to show that such shafts are not needed or employed, but it will be understood that, since gear blanks are normally formed with shaft openings, such gears with shaft openings could be employed, although the openings would serve no purpose in this construction.

The teeth on gears 17, 18 and 19 are only partially shown therearound, in the region of intermeshing engagement, but it is, of course, understood that such teeth are provided completely around the circumference of the gears. The cavities 14, 15 and 16 are substantially identical, and the gears 17, 18 and 19 are substantially identical.

The inlet passage 12 communicates with the intersecting region of cavities 15 and 16 at one side of the region of intermeshing teeth of gears 18 and 19; and inlet pas,-

sageway 13 communicates with the region of intersection of cavities 14 and 15 at one side of the region of intermeshing of the teeth and gears 17 and 18, such communication being at the opposite side from the passage- Way 12.

An outlet passage 241 communicates with the region of intersection of cavities 15 and 16 on the opposite side of the region of intermeshing engagement of gears 18 and 19 from the inlet passage 12. Another outlet passage 21, the same in cross-section as passage 20 and the same as passages 12 and 13, communicates With the region of intersection of cavities 14 and 15 at the op-.

posite side of a point of intermeshing engagement of gears 17 and 18 from passage 13. The direction of flow of fluid through passages 12, 13, 20 and 21, and around the cavities 14, 15 and 16, and the direction of rotation of the intermeshing gears 17, 18 and 19 are shown by' the arrows on Fig. 2.

An outlet chamber 22 is formed in the housing 8 with the opposite ends thereof in communication with the outlet passages 20 and 21. A shuttle piston 23, which is of uniform cross-sectional area and in which the ends are of the same area, is slidably disposed within the chamber 22 for free movement in either direction, depending upon the pressures on opposite sides of the piston 23.

Stops 24 and 25 are formed in the housing at the ends.

of the chamber 22 and project axially thereof toilimit the movement of the piston 23 in either direction.

Referring to Figs. 3 to 5, a commercial form of the flow equalizing device of the present invention is illustrated and, as stated above, the same numerals are used to indicate corresponding elements and passageways as in the diagrammatic showing in Fig. 2.

The housing 8 is formed of three parts, 26, 27 and 28, which have flat adjoining faces and which are held together as an assembled unit by means of screws 29 which pass through aligned openings therein.

The plate 28 is formed with the inlet opening 9 which communicates with a cored dividing passage 39 to divide the flow from the inlet 9 to the passageways 12 and 13 which are also formed in the plate member 28.

l The central section 27 is formed with the intersecting cavities 14, 15 and 16, which are in the form of openings therethrough and which receive the gears 17, 18 and 19 therein for free rotation. This construction makes it possible to finish grind simultaneously the end faces of the central section with the gears in the cavities, thus eliminating chance for error and assuring equal end clearance between all gears and the housing. This eliminates any possibility of variation which would cause unequal slippage of the fluid.

The section 26 is formed with a longitudinal bore therethrough which provides the outlet chamber 22 and which has the shuttle piston 23 mounted therein for free movement. The outlet passageways 20 and 21 are also formed in the member 26 and communicate with the cavities 14, 15 and 16 as in the diagram embodiment above described. The stops 24 and 25 are inserted in the ends of the bore and are provided with seals to prevent leakage and held therein by means of end plugs.

In the operation of the device of the present inventron, fluid under pressure is delivered from a pump (not shown) to the inlet 9. The flow is divided between passages 12 and 13 and is carried around the cavities by the 1ntermeshing gears to the outlet passages 20 and 21, respectively, flowing in the direction of the arrows of Fig. 2 and with the gears rotating in the direction of the arrows shown therein. The fluid passes from the passageways 20 and 21 into the outlet chamber 22 at the opposite ends of the shuttle piston 23 and passes out the outlet ports 10 and 11 into the lines 6 and 7, respectively, to the cylinders.

Assuming that the loads on the pistons of units 2 and 3 are equal, the shuttle piston 23 would remain in its central position and the pressure in passages 20 and 21 would be the same, so that the rate of flow to both of the cylinders 2 and 3 would be the same and the pistons would move in and out in unison and at the same speeds. l-Iowever, assuming, for example, that the load on cyl- 1nder 2 is substantially greater than the load on cylinder 3, as illustrated in Fig. 1, it will be seen that there would be a greater back pressure in chamber 22 on the left side of shuttle 23. If the pressures in passageways 20 and 21 are not equalized, there would he unequal fluid slippage around the gears in the cavities, and there would be unequal delivery to the two cylinders so that the pistons would not move in unison. With the shuttle piston 23 free to move in either direction, depending upon the pressures at the ends, it will be seen that with the greater load on line 6, the piston 23 will move to the right, viewing Fig. 2, causing a restriction in outlet 11, or restricting the flow through passage 20, and thus increasing the pressure in line 20 so that when the shuttle 23 finds its equilibrium position, the pressures in passageways 20 and 21 will be substantially identical. This action is practically instantaneous, and with the pressures in the passageways 20 and 21 the same, the flow delivered through outlets 10 and 11 will be the same and the pistons of units 2 and 3 will move in and out in unison, regardless of unequalities in loads thereon. The shuttle piston, in effect, causes equal slippage, and the pressure drop is negligible because there is no load on the gears except the load due to friction.

In usages where the load unequalities on the two pistons is not great, the shuttle piston may be dispensed with because of the accuracies in manufacture that may be obtained with the construction of the present invention. As pointed out above, this construction eliminates any possibility of variation which would cause unequal slippage of the fluid.

Formal changes may be made in the specific embodiment disclosed without departing from the spirit and substance of the invention, the scope of which is commensurate with the appended'claims.

What is claimed is:

1. A fluid flow equalizing device comprising housing means; first, second and third intersecting cavities formed in said housing means and complementary in shape to gears disposed therein; first, second and third gears disposed in said first, second and third cavities with said first gear in intermeshing relationship with said second gear and said third gear diametrically opposed to said first gear and in intermeshing relationship with said second gear; a fluid inlet passage communicating with the said first and second intersecting cavities at one side of the region of intermeshing teeth of said first and second gears; another fiuid inlet passage communicating with said second and third intersecting cavities at one side of the region of intermeshing teeth of said second and third gears; an outlet passage communicating with said first and second intersecting cavities at the side of the region of intermeshing teeth of said first and second gears opposite to said first-named inlet passage; another outlet passage communicating with said second and third intersecting cavities at the side of the region of intermeshing teeth of said second and third gears opposite to said another inlet passage; an outlet chamber having a shuttle piston therein and communicating with said outlet passages on opposite sides of said piston; and a pair of outlet ports communicating with said outlet chamber on opposite sides of said piston.

2. A fluid fiow equalizing device comprising housing means; first, second and third intersecting cavities formed in said housing means and complementary in shape to gears disposed therein; first, second and third gears freely disposed in said first, second and third cavities with said first gear in intermeshing relationship with said second gear and said third gear diametrically opposed to said first gear and in intermeshing relationship with said second gear; a fluid inlet passage communicating with the said first and second intersecting cavities at one side of the region of intermeshing teeth of said first and second gears; another fluid inlet passage communicating with said second and third intersecting cavities at one side of the region of intermeshing teeth of said second and third gears; an outlet passage communicating with said first and second intersecting cavities at the side of the region of intermeshing teeth of said first and second gears opposite to said first-named inlet passage; another outlet passage communicating with said second and third intersecting cavities at the side of the region of intermeshing teeth of said second and third gears opposite to said another inlet passage, an outlet chamber having a shuttle piston therein and communicating with said outlet passages on opposite sides of said piston; and a pair of outlet ports communicating with said outlet chamber on opposite sides of said piston.

3. A fluid flow equalizing device comprising housing means; first, second and third intersecting cavities formed in said housing means and complementary in shape to gears disposed therein; first, second and third gears disposed in said first, second and third cavities with said first gear in intermeshing relationship with said second gear and said third gear diametrically opposed to said first gear and in intermeshing relationship with said econd gear; a fluid inlet passage communicating with the said first and second intersecting cavities at one side of the region of intermeshing teeth of said first and second gears; another fluid inlet passage communicating with of said second and third gears opposite to said another said second and third intersecting cavities at one side of inlet passage.

the region of intermeshing teeth of said second and third gears; an outlet passage communicating with said first and Refflencfis Cited in the file of this Patent second intersecting cavities at the side of the region of 5 UNZTED STATES PATENTS intermeshing teeth of said first and second gears opposite to said first-named inlet passage; and another outlet pas-' 236L095 Mluer et 1944 sage communicating with said second and third intersect- 2466485 Schultz 1949 2,628,629 Deardorfi Feb. 17, 1953 ing cavities at the side of the region of intermeshing teeth 

